Large inkjet printers are well developed and known that the ejected inks under an appropriate curing process would appear highly desirable and afford a tough, durable image upon print media to which they are applied. This makes the large inkjet printers especially applicable to printing on various print media with different properties or thickness such as plastics packaging, conventional cellulosic substrates and synthetic polymeric substrates. Thus, large inkjet printers can make images more easily, more quickly and more inexpensively than the gravure printing system with a pre-processing taking much cost and times.
In the conventional large inkjet printer, print media receiving the printed image rests on a horizontally extending sliding table, which is situated below a movable carriage carrying a printing module. The printing module includes a plurality of ink containers and a plurality of ink cartridges in fluid communication with the containers, with each cartridge provided with a bottom nozzle to emit droplets of differently colored ink onto the print media. Thus, the inkjet printing module is controlled by a computer which is programmed to moved along a carriage track across the sliding table and energize nozzles of print heads as the printing module traverses across the print media. The ink droplets on the print media is then cured by curing devices, such as an ultraviolet irradiator device, to provide the desired final image.
Various print media of different characteristics (e.g., thickness and hardness) can be applied and printed by the large inkjet printer, and the altitude of printing module above the print media needs to be readjusted in accordance with characteristics of the print media, such that the distance between nozzles of print heads and the print media can remain in an optimum degree for printing. In the beginning of the printing reproduction operation, operators need to prepare proof printing which comprises adjusting the distance of the printing module to the print media and emitting ink droplets to a print media, before the actual reproduction operation, to adjust the printing module to a proper height and verify if the layout is as desired. However, the preparation of this proof will increase the production time and printing cost, and this may be economically disadvantageous when the printing media is an expensive material. On the other hand, this proof process may damage the nozzles when the printing module is over-lowered causing the nozzles to knock against the print media.
Accordingly, there is a need for an improved large inkjet printer to preset the altitude of printing module above the print media to reduce cost and make a high throughput to overcome the shortcomings of the prior art.